The present invention relates generally to circuit condition monitoring devices for use in electrical power distribution systems, and in particular to a clamp mechanism for clamping such devices to the various sized cables of such systems.
Electrical power distribution systems typically require the use of a variety of monitoring devices to facilitate the detection and location of system malfunctions. Among such devices are manual and automatic reset fault current indicators, and voltage monitoring devices. These devices are typically either mounted on a test point provided on a system component, or clamped directly onto a cable of the system.
Clamp-on mounting devices typically include a housing which contains the monitoring device, a circuit condition indicator, and some form of clamping mechanism for mounting the housing on a cable. Since power cables used in the industry are routinely of various diameters, it is necessary that the clamping mechanism accommodate a range of cable diameters.
In one prior clamp mechanism, which is described in U.S. Pat. No. 4,456,873 of the present inventor, a plurality of flexible metallic strips are combined to form a generally square-shaped core for use with a circuit condition monitoring device. One end of the core is fixedly positioned relative to the device housing, and the opposite end is detachably engaged to the one end. In use, the opposite end is displaced from the engagement, allowing the core to be passed around a cable.
Another prior clamp mechanism, which is described in U.S. Pat. No. 4,646,006, also of the present inventor, includes a pair of clamp members biased for engaging movement toward one another. A compression member between the clamp members ordinarily prevents engaging movement of the members. When pressed against a cable, the compression member deforms to allow the clamp members to move toward one another and encircle the cable and clamp a monitoring device thereon.
The present invention is directed to a clamp mechanism having a resilient core and a device housing having a cable engaging surface wherein a spring extends between the core portions on either side of the conductor to bias the conductor into engagement with the engaging surface. The spring is slidably attached at one end to a bridging element which allows the spring to slide and thereby extend less in accommodating cables of varying diameters. This enables the same clamp and spring to be used for a wide range of cable diameters.
Accordingly, it is a general object of the present invention to provide a new and improved clamp mechanism for a circuit monitoring device.
It is a more specific object of the present invention to provide a clamp mechanism for clamping a circuit condition monitoring device to the cable of a power distribution system wherein the cable has a range of diameters.